fix: prevent race conditions for concurrent npm-based server processes using same node_modules dir

[simschla]

In #2462 and #2542 we added support for multiple npm-based formatters sharing the same node_modules directory.
In my projects I noticed that - every once in a while - some of the npm-server-processes failed to start. This happened more often when configuration cache was active (and hence processes started faster). The lint files showed the following messages (example):

Process result:
> arguments: [/path/to/repo/.gradle/nodejs/node-v24.11.1-darwin-arm64/bin/npm, start, --scripts-prepend-node-path=true, --, --node-server-instance-id=d61a85af-5417-40d9-9fa7-369ded8b7921]
> exit code: 0
>    stdout: (below)
> npm warn Unknown cli config "--scripts-prepend-node-path". This will stop working in the next major version of npm.
> 
> > spotless-prettier@4.0.0 start
> > node serve.js --node-server-instance-id=***
> 
> [Error: ENOENT: no such file or directory, rename 'server.port.tmp' -> 'server-d61a85af-5417-40d9-9fa7-369ded8b7921.port'] {
>   errno: -2,
>   code: 'ENOENT',
>   syscall: 'rename',
>   path: 'server.port.tmp',
>   dest: 'server-d61a85af-5417-40d9-9fa7-369ded8b7921.port'
> }

This PR fixes this race condition by making sure that the server-processes do not collide on the server.port.tmp file anymore, no matter the timing.

[Copilot]

Pull request overview

This PR fixes a race condition that occurred when multiple npm-based formatters (prettier, eslint, tsfmt) launch their server processes simultaneously while sharing the same node_modules directory. The issue manifested as "ENOENT: no such file or directory, rename 'server.port.tmp'" errors because concurrent processes were colliding on the shared temporary filename.

Key Changes:

• Fixed race condition by including the instance ID in the temporary port filename
• Bumped npm package versions from 4.0.0 to 4.0.1 for all three formatters
• Updated changelog entries across all affected components

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
lib/src/main/resources/com/diffplug/spotless/npm/common-serve.js	Core fix: changed server.port.tmp to use instance-specific filenames like server-{instanceId}.port.tmp to prevent concurrent access collisions
lib/src/main/resources/com/diffplug/spotless/npm/eslint-package.json	Version bump from 4.0.0 to 4.0.1 to reflect the bug fix
lib/src/main/resources/com/diffplug/spotless/npm/prettier-package.json	Version bump from 4.0.0 to 4.0.1 to reflect the bug fix
lib/src/main/resources/com/diffplug/spotless/npm/tsfmt-package.json	Version bump from 4.0.0 to 4.0.1 to reflect the bug fix
CHANGES.md	Added entry documenting the race condition fix
plugin-gradle/CHANGES.md	Added entry documenting the race condition fix for gradle plugin users
plugin-maven/CHANGES.md	Added entry documenting the race condition fix for maven plugin users

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